With the advance of techniques for fabricating thin-film transistors, the flat panel displays (FPD) are widely applied in electrical products, such as PDAs, laptops, digital cameras, cell phones, etc. due to advantages as portability, non-radiation and lower power consumption. Especially when the manufacturers devote themselves to further research and improve the materials, processes and equipments, the qualities of FDP devices are promoted and the production costs thereof are reduced substantially.
In general, on these electronic products, such as PDAs or notebook, are assembled with keyboards for providing consumers to input data and orders. However, following the current design trend of the electronic products towards portable and practical, the keyboards occupied the part space of the electronic products usually hinder from the portability. Therefore, touch screens are introduced to some electronic products.
In the conventional touch screens, a touch panel is fabricated on a display to provide consumers for inputting data and orders by utilizing a hand-held stylus in conjunction with the touch screen display. However, because it is indispensable to fabricate the touch panel onto the outer surface of display, some light source is obstructed, and thus the image displaying efficiency is decreased. Even though the transparency of the touch panel in current products is promoted about 85%, for most electronic products with touch panels, the extra backlight sources are still required to provide enough illumination. And the transparency limitation of the touch panels also squander lots of electrical power.
For thoroughly solving the above problems, the display manufacturers introduce digitizers to substitute for the conventional touch screen. Please refer to FIG. 1, a liquid crystal display 10 integrated with a digitizer 40 is illustrated. The liquid crystal display 10 comprises a display module 20, a backlight unit 30 and the digitizer 40. The display module 20 has an upper glass substrate 22, a lower glass substrate 24, and a liquid crystal molecule layer inserted therebetween. On the upper glass substrate 22 an upper polarizer 26 is fabricated, and beneath the lower glass substrate 24 a lower polarizer 26 is fabricated. Specially, a printed circuit board assembly (PCB assembly) 27 is electrically connected to the lower glass substrate 24 via a flexible printed circuit board (FPC) 29 for driving the thin film transistors on the lower glass substrate 24. By using a timing control chip 25 fabricated on the PCB assembly 27, the thin film transistors can be switch on or off.
Besides, the backlight module 30 comprises a lightguide 32, optical films 34, a white sheet 36, a lamp 38 and a reflector cover 39. The lightguide 32 made of acrylics is applied to provide light propagating paths. Aside the lightguide 32 disposed the lamp 38 is applied to illuminate the lightguide 32 in the edgelight form. The lights entering from one side of the lightguide 32 can propagate therethrough to another side in the total reflection form. Aside the lamp 38 the reflector cover 39 is applied to prevent illumination from dissipating. The white sheet 36 is placed beneath the lightguide 32 to reflect the light dispersed from the lightguide 32. And the optical films 34 disposed on the lightguide 32 including some diffuser films and brightness enhancing films are introduced to make the light scattering more uniformly.
The digitizer 40 comprises a sensor board 42 and a control board 44. The sensor board 42 has the grid type of antenna arrays and is mounted underneath the backlight unit 30. When consumers utilize a hand-held stylus to select or input data above the display module 20, the sensor board 42 can receive the electromagnetic signals and transfer these signals to the control board 44 via a connecting bus 46. Then the control board 44 can decode these signals and communicate with the motherboard of the electronic product. On the control board 44 an ASIC chip 48 is fabricated for providing the above decoding and communicating functions.
It is noted that after assembling the display module 20 and the backlight unit 30, the FPC board 29 is wound around the sidewall of the backlight unit 30 to have the drive circuit board 27 attached to the lower surface of the backlight unit 30 for saving space. However, after integrating the digitizer 40 into the display, if the sensor board 42 is disposed under the drive circuit board 27, the electronic signals passing on the drive circuit board 27 will severely interfere with the signals received by the antenna arrays of the sensor board 42. Therefore, as shown in FIG. 2, in the current displays, the sensor board 42 is inserted between the drive circuit board 27 and the backlight unit 30, and which is screwed or taped to fasten onto the backlight unit 30 for preventing from the signal interference of the drive circuit board 27. However, after that, the thickness of the display is increasing, and thus it is indispensable to prolong the FPC board 29 for inserting the sensor board 42 between the drive circuit board 27 and the backlight unit 30.